1. Field of the Invention
The present invention relates to dihydropyran derivatives, to processes for preparing these derivatives and to processes for preparing vitamin intermediates, in particular vitamins A and E intermediates, using the dihydropyran derivatives.
2. Description of the Art
According to Japanese Patents J53-101308 and J53-101309, vitamin A intermediates may be prepared by the hydrolysis of dihydropyran derivatives bearing an alkyl radical at the 4-position and optionally a hydroxyl group at the 2-position. The process for preparing these derivatives is carried out by the hydrogenation of a hydroperoxide on a palladium- or platinum-based catalyst. However, dihydropyran derivatives substituted at the 6-position with a polyene chain can not be obtained with the prior art process.